import java.util.Scanner;

public class sum {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        System.out.println("请输入成绩");
        double i = s.nextDouble();
        if(0<i&&i<60){
            System.out.println("c");
        }
        if(i<=80){
            System.out.println("b");
        }
        if(i<=100){
            System.out.println("a");
        }else{
            System.out.println("您输入的成绩有误，请重新输入");
        }

    }
}
